(p, Vm, T) and phase equilibrium measurements for a natural gas-like mixture using an automated isochoric apparatus

We have developed an automatic apparatus for measuring phase equilibrium and (p, V_m, T) properties of gas mixtures in our laboratory. Based upon the isochoric method, the apparatus can operate at temperatures ranging from 100 K to 500 K at pressures up to 35 MPa, and yield absolute results in fully automated operation. Temperature measurements are accurate to 0.01 K and pressure measurements are accurate to 0.002 MPa. The isochoric method utilizes pressure versus temperature measurements along an isomole (near isochore) and detects phase boundaries by locating the change in the slope of the isomoles.We also have developed a strategy that allows us, when using the above isochoric method together with a second apparatus capable of isothermal density measurements, to collect derived densities that are competitive in accuracy with those of the densimeter, but with a procedure and design that is easy to automate. We present data on a natural gas-like mixture. The experimental data indicate that prediction of the dew point curve with current equations of state is unreliable.     

锂离子电池正极材料LiMn2O4的合成与晶体结构（英）

Spinel LiMn₂O₄ powders were prepared using two-step synthesis method consisting of solid-state reaction method and citrate modified sol-gel method. The effects of the calcination temperature and the Li/Mn ratio of raw materials were studied on the physicochemical and electrochemical properties of the spinel LiMn₂O₄ powders, such as crystallinity, lattice constant and density. The title compound was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Polycrystalline LiMn₂O₄ powers calcined at 750 ℃ were found to be composed of very uniformly-sized microcrystal with an average particle size of 300 nm. The improvement in electrochemical properties was mainly attributed to the process of re-grinding by absolute alcohol.     

An electrochemical immunosensor based on agarose hydrogel films for rapid determination of ractopamine

A novel label-free electrochemical immunosensor for rapid determination of ractopamine was constructed by incorporating ractopamine–bovine thyroglobulin antigen in agarose hydrogel films modified on a glassy carbon electrode. Cyclic voltammetry and differential pulse voltammetry were employed to investigate the electrochemical character of the immunosensor during different modified stages using a redox probe system of K₃Fe(CN)₆/K₄Fe(CN)₆. In the presence of polyclonal antibody against ractopamine, K₃[Fe(CN)₆] electron transfer is inhibited, presumably due to that antibody in solution could adsorb on the electrode surface modified antigen. A competitive immunoreaction system was applied to determinate the free ractopamine in phosphate buffer solution. The selected polyclonal antibody showed very high sensitivity and specificity for ractopamine, and was used for the detection and quantitative determination of trace amounts of ractopamine in spiked animal feeds.     

An infrared study on Langmuir–Blodgett films of 14,15-bis(hydroxyimino)-13-thiaoctacosane

The Langmuir–Blodgett (LB) films of 14,15-bis(hydroxyimino)-13-thiaoctacosane (TOC) on aluminium plated substrates were investigated using Fourier transform infrared (FTIR), grazing angle (GAIR) and horizontal attenuated total reflectance (HATR) techniques. The LB films of TOC can be transferred onto the solid substrate successfully. The molecular structure of LB films was analysis by comparing the GAIR and HTAR spectra. The intense bands at 2848 and 2918 cm⁻¹ are assigned to symmetric ν_s(CH₂) and asymmetric ν_a(CH₂) stretching vibrations of methylene groups. These peaks suggest that the alkyl chains in TOC are nearly in all-trans conformational state. The presence in the infrared spectra of several bands due to the methylene wagging and twisting modes and of the splitting of the bands due to the methylene scissoring mode at 1467 and 1459 cm⁻¹ and the CH₂ rocking mode at 720 and 731 cm⁻¹ also indicates that in films of TOC alkyl chains are in the all-trans conformation and packed in either an orthorhombic or a monoclinic structure with an orthorhombic subcell containing two mutually orthogonal molecules. Another conclusion presented in this paper that the alkyl chain tilt, which is the angle between the axis, which bisects the C–C bonds and the surface normal, was quite large by comparing the GAIR and HATR spectra.     

Thermal characterization and thermal degradation of poly(norbornene-2,3-dicarboxylic acid dialkyl esters) synthesized by vinyl addition polymerization

The thermal properties and degradation behaviors of poly(norbornene-2,3-dicarboxylic acid dialkyl esters) (PNB-dialkyl esters) (alkyl = Me (PNB-Me), Et (PNB-Et), Pr (PNB-Pr), and Bu (PNB-Bu)) were investigated by thermogravimetric analysis (TGA) in dynamic conditions and by infrared (IR) spectroscopy. The PNB-dialkyl esters show good thermal stability up to 350 °C, and the thermal stability decreases in the order Me > Et > Pr > Bu with the increase in size of side chain. The effect of side-chain size on the thermal degradation behaviors of PNB-dialkyl esters is evidenced by one-step thermal degradation profile for PNB-Me while two-step thermal degradation profile for PNB-Et, PNB-Pr, and PNB-Bu. Transformation is deduced to undergo β-hydrogen elimination and formation of anhydride group in the first stage of thermal degradation reaction according to TGA and IR results for PNB-Et, PNB-Pr, and PNB-Bu. The apparent activation energy and thermal degradation model of PNB-dialkyl esters are estimated by means of Ozawa-Flynn-wall method and Phadnis-Deshpande method, respectively.     

Influence of extended π-conjugation units on carrier mobilities in conducting polymers

Carrier mobilities in thin films of copolymers with repeat units consisting of oligothiophenes bridged by Si atoms are measured over a range of doping levels, where the numbers of thienylenes in the repeat unit are 7, 8, 10, 12, and 14. The mobilities for these polymer films increased with the increase in doping level and the mobility enhancement followed an increasing order of the π-conjugation length. The magnitude of the mobility increase for the Si polymer comprising 14 thiophene units reached ca. 10⁴, implying that this π-conjugation length is almost sufficient to reproduce transport properties of polythiophenes.     

Small copper nanoclusters: X-ray absorption analysis

X-ray absorption near edge structure (XANES) spectra at the cooper L_2,3-edge of small cooper nanoclusters has been studied. Theoretical interpretation of XANES spectra measured for small copper nanoclusters have been performed. Theoretical analysis is based on a self-consistent full multiple scattering theory of X-ray absorption as well as on non-muffin-tin finite difference method (FDM). This approach allows choosing the best model for local geometry of small cooper nanoclusters.     

Direct electrochemistry and electrocatalysis of hemoglobin in gelatine film modified glassy carbon electrode

Direct electrochemical and electrocatalytic behavior of hemoglobin (Hb) immobilized on glass carbon electrode (GCE) containing gelatine (Gel) films was investigated. The characteristics of Hb/Gel film modified GC electrode were performed by using SEM microscopy, UV-vis spectroscopy and electrochemical methods. The immobilized Hb showed a couple of quasi-reversible redox peak with a formal potential of −0.38 V (versus SCE) in 0.1 M pH 7.0 PBS. The formal potential changed linearly from pH 4.03 to 8.41 with a slope value of −52.0 mV pH⁻¹, which suggested that a proton transfer was accompanied with each electron transfer (ET) in the electrochemical reaction. The Hb/gelatine/GCE displayed a rapid amperometric response to the reduction of H₂O₂ and nitrite.     

Behaviour of organic pollutants in paper and board samples intended to be in contact with food

This paper deals with the study of volatile compounds present in a set of three paper and board (P&B) samples of different composition, surface treatment, grammage and thickness. The volatile compounds released by the packaging material (P&B) can be trapped on the food and may then affect the safety and health of consumers. To evaluate if the recycled P&B could be used as food packaging material, adsorption studies have been performed with a selection of chemical substances. The adsorption isotherms are provided. Partition coefficients between paper and air have been calculated for a series of volatile compounds used as model compounds to represent different families of contaminants commonly present in P&B. Values from 4 to 3243 were obtained at different temperatures. The analysis of volatile compounds have been carried out by automatic headspace coupled on-line with GC/MS in SIM mode. The results obtained are shown and discussed.     

Asymmetric palladium-catalyzed benzylic nucleophilic substitution: high enantioselectivity with the DUPHOS family ligands

The asymmetric palladium-catalyzed benzylic reaction of 1-(2-naphthyl)ethyl acetate and its 6-methoxy substituted analogue with dimethyl malonate anion led to substitution products with up to 90% ee when the iPr-DUPHOS chiral ligand was used.